diff --git a/dom/base/nsObjectLoadingContent.cpp b/dom/base/nsObjectLoadingContent.cpp
index f3dba17f7c..f46c1d3e7e 100644
--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -1473,113 +1473,6 @@ nsObjectLoadingContent::CheckJavaCodebase()
   return true;
 }
 
-void
-nsObjectLoadingContent::MaybeRewriteYoutubeEmbed(nsIURI* aURI, nsIURI* aBaseURI, nsIURI** aOutURI)
-{
-  nsCOMPtr<nsIContent> thisContent =
-    do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
-  NS_ASSERTION(thisContent, "Must be an instance of content");
-
-  // We're only interested in switching out embed and object tags
-  if (!thisContent->NodeInfo()->Equals(nsGkAtoms::embed) &&
-      !thisContent->NodeInfo()->Equals(nsGkAtoms::object)) {
-    return;
-  }
-  nsCOMPtr<nsIEffectiveTLDService> tldService =
-    do_GetService(NS_EFFECTIVETLDSERVICE_CONTRACTID);
-  // If we can't analyze the URL, just pass on through.
-  if(!tldService) {
-    NS_WARNING("Could not get TLD service!");
-    return;
-  }
-
-  nsAutoCString currentBaseDomain;
-  bool ok = NS_SUCCEEDED(tldService->GetBaseDomain(aURI, 0, currentBaseDomain));
-  if (!ok) {
-    // Data URIs (commonly used for things like svg embeds) won't parse
-    // correctly, so just fail silently here.
-    return;
-  }
-
-  // See if URL is referencing youtube
-  if (!currentBaseDomain.EqualsLiteral("youtube.com")) {
-    return;
-  }
-
-  // We should only rewrite URLs with paths starting with "/v/", as we shouldn't
-  // touch object nodes with "/embed/" urls that already do that right thing.
-  nsAutoCString path;
-  aURI->GetPath(path);
-  if (!StringBeginsWith(path, NS_LITERAL_CSTRING("/v/"))) {
-    return;
-  }
-
-  // See if requester is planning on using the JS API.
-  nsAutoCString uri;
-  aURI->GetSpec(uri);
-  if (uri.Find("enablejsapi=1", true, 0, -1) != kNotFound) {
-    return;
-  }
-
-  // Some YouTube urls have parameters in path components, e.g.
-  // http://youtube.com/embed/7LcUOEP7Brc&start=35. These URLs work with flash,
-  // but break iframe/object embedding. If this situation occurs with rewritten
-  // URLs, convert the parameters to query in order to make the video load
-  // correctly as an iframe. In either case, warn about it in the
-  // developer console.
-  int32_t ampIndex = uri.FindChar('&', 0);
-  bool replaceQuery = false;
-  if (ampIndex != -1) {
-    int32_t qmIndex = uri.FindChar('?', 0);
-    if (qmIndex == -1 ||
-        qmIndex > ampIndex) {
-      replaceQuery = true;
-    }
-  }
- 
-  // If we're pref'd off, just return.
-  if (!Preferences::GetBool(kPrefYoutubeRewrite)) {
-    return;
-  }
-
-  nsAutoString utf16OldURI = NS_ConvertUTF8toUTF16(uri);
-  // If we need to convert the URL, it means an ampersand comes first.
-  // Use the index we found earlier.
-  if (replaceQuery) {
-    // Replace question marks with ampersands.
-    uri.ReplaceChar('?', '&');
-    // Replace the first ampersand with a question mark.
-    uri.SetCharAt('?', ampIndex);
-  }
-  // Switch out video access url formats, which should possibly allow HTML5
-  // video loading.
-  uri.ReplaceSubstring(NS_LITERAL_CSTRING("/v/"),
-                       NS_LITERAL_CSTRING("/embed/"));
-  nsAutoString utf16URI = NS_ConvertUTF8toUTF16(uri);
-  nsresult rv = nsContentUtils::NewURIWithDocumentCharset(aOutURI,
-                                                          utf16URI,
-                                                          thisContent->OwnerDoc(),
-                                                          aBaseURI);
-  if (NS_FAILED(rv)) {
-    return;
-  }
-  const char16_t* params[] = { utf16OldURI.get(), utf16URI.get() };
-  const char* msgName;
-  // If there's no query to rewrite, just notify in the developer console
-  // that we're changing the embed.
-  if (!replaceQuery) {
-    msgName = "RewriteYoutubeEmbed";
-  } else {
-    msgName = "RewriteYoutubeEmbedInvalidQuery";
-  }
-  nsContentUtils::ReportToConsole(nsIScriptError::warningFlag,
-                                  NS_LITERAL_CSTRING("Plugins"),
-                                  thisContent->OwnerDoc(),
-                                  nsContentUtils::eDOM_PROPERTIES,
-                                  msgName,
-                                  params, ArrayLength(params));
-}
-
 bool
 nsObjectLoadingContent::CheckLoadPolicy(int16_t *aContentPolicy)
 {
@@ -1836,14 +1729,6 @@ nsObjectLoadingContent::UpdateObjectParameters(bool aJavaURI)
                                                    uriStr,
                                                    thisContent->OwnerDoc(),
                                                    newBaseURI);
-    nsCOMPtr<nsIURI> rewrittenURI;
-    MaybeRewriteYoutubeEmbed(newURI,
-                             newBaseURI,
-                             getter_AddRefs(rewrittenURI));
-    if (rewrittenURI) {
-      newURI = rewrittenURI;
-      newMime = NS_LITERAL_CSTRING("text/html");
-    }
 
     if (NS_SUCCEEDED(rv)) {
       NS_TryToSetImmutable(newURI);
diff --git a/dom/base/nsObjectLoadingContent.h b/dom/base/nsObjectLoadingContent.h
index a267f01898..c9b786eeb6 100644
--- a/dom/base/nsObjectLoadingContent.h
+++ b/dom/base/nsObjectLoadingContent.h
@@ -504,30 +504,6 @@ class nsObjectLoadingContent : public nsImageLoadingContent
      */
     nsPluginFrame* GetExistingFrame();
 
-    /**
-     * Used to try to rewrite a youtube flash embed to HTML5 player
-     *
-     * aRewrittenURI is filled with the result of rewriting
-     * if plugin.rewrite_youtube_embeds pref is true and
-     * the element this nsObjectLoadingContent instance represents:
-     *
-     * - is an embed or object node
-     * - has a URL pointing at the youtube.com domain, using "/v/" style video
-     *   path reference, and without enablejsapi=1 in the path
-     *
-     * Having the enablejsapi flag means the document that contains the element
-     * could possibly be manipulating the youtube video elsewhere on the page
-     * via javascript. We can't rewrite these kinds of elements without possibly
-     * breaking content, which we want to avoid.
-     *
-     * If we can rewrite the URL, we change the "/v/" to "/embed/", and change
-     * our type to eType_Document so that we render similarly to an iframe
-     * embed.
-     */
-    void MaybeRewriteYoutubeEmbed(nsIURI* aURI,
-                                  nsIURI* aBaseURI,
-                                  nsIURI** aRewrittenURI);
-
     // Helper class for SetupProtoChain
     class SetupProtoChainRunner final : public nsIRunnable
     {